This invention relates generally to signal processors and more particularly to ranging and depth finding (sonar) signal processors.
As is known in the art, ranging and depth finding systems generally rely upon detecting a received signal by using matched filter or correlation techniques to improve the signal to noise ratio of the received signal i.e. the signal power relative to the power in the received background noise produced by the medium through which the signal propagates. In the case of a sonar system, sea water in the propagation medium between a receiving transducer and the seabed reflecting the transmitted wave. The sea water may produce background noise comparable in power to the power of the signal. Coding of the transmitted signal and matched filter detection are often employed to improve the signal to noise ratio of the received signal. However, abnormalities in the propagation medium or of the reflecting seabed cause distortion of the received signal thereby reducing the effectiveness of the matched filter in providing optimum signal to noise ratio detection. The degree of the distortion is related to the slope of the portion of the seabed reflecting the transmitted wave relative to the wavefront of such transmitted wave. When a signal is reflected from such a sloping surface, the reduction in correlation reduces the signal to noise ratio. Further, at extreme conditions, detection of the reflected signal is not possible.